1. Field
This disclosure is concerned generally with the field of fermentation and specifically with the use of photometabolically active microorganisms to produce molecular hydrogen from water.
2. Prior Art
As pointed out in the above-cited patent, the disclosures of which are incorporated herein by reference thereto, it is well known that certain microorganisms are capable of producing useful products in the presence of light and certain substrates. The disclosed photometabolically active systems are concerned primarily with using a single type of microorganism to produce products such as H.sub.2, ATP, and NADPH on a continuous basis. Although multiple organism systems are disclosed, no actual examples are shown.
Thus, that patent generally describes a method for the continuous photometabolic production of a useful product which consists in immobolizing whole cells of a photometabolically active organism on a medium to form a stabilized composite, supportably placing the composite within a reactor having at least one light transmitting wall, and, in the presence of light being transmitted through the wall, continuously passing into the reactor a substance capable of being photometabolized by the cells under conditions sufficient to assure the production of the useful product. The specification discloses two particularly preferred inventive embodiments. In the first, an aqueous malate solution constitutes the substance being photometabolized, molecular hydrogen as the product being formed, bacterial cells as the whole cells, and the immobilizing medium as a gel-like material. In the second, Blue-Grass algae are similarly stabilized for the continuous biophotolysis of water by oxidizing the water and reducing NADP to NADPH. In those preferred embodiments, Rhodospirillium rubrum comprise the operable bacterial cells, Anacystis nidulans constitute the operable algae cells, and agar provides the operable gel-like material.
In work done subsequent to that which was the basis for the above application, I have found an improved method for the biophotolysis of water and the production of H.sub.2 gas. This method is based on the use of two systems of microorganisms and the continuous recycling of a reduceable cofactor such as nicotine-adenine-dinucleotide phosphate (NADP) through both systems. Details of the method are described below.